1. Field of the Invention
The present invention relates to a device for replacing printing plates in rotary printing presses having plate cylinders. The plate cylinders receive both ends of a printing plate in the cylinder gap while the surface of the printing plate is wound around the plate cylinder. The device has a facility for taking a printing plate from the plate cylinder after it has been released by the clamping devices of the plate cylinder and a facility for feeding a new printing plate to the plate cylinder.
2. Description of the Related Art
European Patent Application No. 0 433 798 discloses a method and a device for automatic feeding and/or removing of printing plates. This device is provided with a storage section for receiving a printing plate to be removed from a plate cylinder before a new printing plate is clamped on the plate cylinder. In close vicinity to the plate cylinder receiving the printing plates there are provided transport and pressure rollers in order to ensure exact feeding of the printing plate front edge. However, the newly supplied printing plate as well as the printing plate to be removed from the plate cylinder, for the greater part of their transport path, are moved over resting surfaces, so that scratching of the highly sensitive surfaces of the supplied and removed printing plates can still occur.
European Patent Application No. 0 432 660 also discloses a method and device for automatic replacement of a printing plate. The device for implementing the method includes a number of transport rollers disposed between the storage sections for the printing plates. Between the transport rollers and the surface of the plate cylinder or the wide cylinder gap there are arranged a movable discharge finger and a guide plate. This construction has an elaborate, costly mechanism which also impairs access to the printing units of a rotary printing press.
The European Patent Application No. 0 570 702 shows a device for supplying printing plates to the plate cylinder of printing presses, particularly sheet-fed offset presses. This device includes an angular sheet-metal plate which is operable by a pneumatic cylinder, whereby the plate profile is pressed against brushes. Through the space formed between the sheet-metal plate profile and the brushes, a new printing plate can be fed directly into the clamping bar of a plate cylinder. There is no mention made about the handling of a printing plate to be removed from the plate cylinder before a new printing plate is fed to the plate cylinder in that application. The teachings of this prior art document are concentrated on the simplification of the feed of the printing plate front edge.
European Patent Application No. 0 431 715 a shows further plate-changing device for printing presses. This device relates to sheet-fed rotary printing presses and includes a storage section for a new printing plate to be fed as well as for the printing plate released form the plate cylinder. This device is defined by a cassette which holds multiple printing plates, the cassette being pivotally mounted between the serially-arranged printing units of a sheet-fed rotary press. In the cassette there are multiple L-shaped hooks with which the individual printing plates can be fastened in the cassette, so that considerable mechanical expenditure has to be made for the storage of printing plates in a pivotable cassette.